Martin Cowie

The synthesis of some binuclear ruthenium (I) complexes bridged by anionic groups. X-ray structures of pyrazolate- and oxypyridinate-bridged complexes

A series of binuclear ruthenium(I) complexes, [Ru2(CO)4(μ-XY)2(PPh3)2], have been prepared by two closely related routes. Complexes 2 (XY− = S2NC3H4−) and 3 (XY− = NC5H4O−) have been prepared by the reaction of [Ru2(CO)4(O2-CCH3)2(PPh3)2] with sodium 2-mercaptothiazolinate and sodium 2-oxypyridinate, respectively. The related pyrazolate-bridged complex 4 (XY−=N2C3H3−) was prepared by the reaction of sodium pyrazolate with [Ru2(CO)4(O2CCH3)(NCMe)2] followed by addition of PPh3. The X-ray structures of compounds 3 and 4 have been determined. Compound 3 crystallizes in the triclinic space group P1 with a 14.766(2), b 15.821(2), c 10.745(3) A, α 98.28(2)°, β 110.99(2)°, γ 103.29(1)°, V 2209.1 A3, Z = 2. On the basis of 5521 unique observations (tNO) and 379 parameters varied (NV) the structure has been refined to R = 0.042 and Rw = 0.054. Compound 4 crystallizes in the orthorhombic space group P212121 with a 13.220(2), b 14.846(4), c 21.403(3) A, V 4200.7 A3 and Z = 4. This structure has been refined to R = 0.041 and Rw = 0.023 for NO = 3915 and NV = 546. Both structures display the sawhorse arrangement of carbonyl groups and have the phosphine ligands in the axial positions opposite the RuRu bonds. For 3 the oxypyridinate groups are bound in a head-to-tail arrangement. The two-atom pyrazolate bridge imparts more strain than the three-atom oxypyridinate bridge and as a result the equatorial planes of the Ru centers are tipped by only 16.2(4)° in 3 but by 35.4(1)° in 4. The RuRu distances (2.7108(4) A (3); 2.732(1) A (4)) correspond to normal single bonds.

The structure of [(PPh3)PdFe(SC5H4)2]•0.5C6H5CH3: an unusual heterobinuclear complex containing a weak Fe→Pd dative bond

Abstract The structure of [(PPh 3 )PdFe(SC 5 H 4 ) 2 ]·0.5C 6 H 5 CH 3 has been determined by X-ray crystallography. This compound crystallizes in the monoclinic space group C 2/ c with a 39.258(5), b 10.548(2), c 13.612(4) A, β 101.69(2)°, V 5519.7 A 3 and Z = 8. On the basis of 3255 unique observations the structure has refined to R = 0.040 and R w = 0.046. The complex is an unusual heterobinuclear FePd species in which the two metals are held together by the bridging cyclopentadienethiolato groups and what appears to be a dative Fe → Pd bond (2.878(1) A).

The Bridged Binding Mode as a New, Versatile Template for the Selective Activation of Carbon−Fluorine Bonds in Fluoroolefins: Activation of Trifluoroethylene

We report the selective activation of carbon-fluorine bonds in trifluoroethylene using the diiridium complex [Ir(2)(CH(3))(CO)(2)(dppm)(2)][OTf] (1). Coordination of trifluoroethylene in a bridging position between the two metals in 1 results in facile fluoride ion loss in three different ways. Attack by strong fluorophiles such as Me(3)SiOTf and HOTf results in F(-) removal from one of the geminal fluorines to give the cis-difluorovinyl-bridged product [Ir(2)(CH(3))(OTf)(CO)(2)(μ-κ(1):η(2)-C(F)═CFH)(dppm)(2)][OTf]. A second activation can also be accomplished by addition of excess Me(3)SiOTf to give the fluorovinylidene-bridged product [Ir(2)(CH(3))(OTf)(CO)(2)(μ-C(2)FH)(dppm)(2)][OTf](2). Interestingly, activation of the trifluoroethylene-bridged precursor by water also occurs, yielding [Ir(2)(CH(3))(CO)(2)(κ(1)-C(H)═CF(2))(μ-OH)(dppm)(2)][OTf], in which the lone vicinal fluorine is removed, leaving a geminal arrangement of fluorines in the product. A [1,2]-fluoride shift can also be induced in the trifluoroethylene-bridged precursor upon the addition of CO to give the 2,2,2-trifluoroethylidene-bridged product [Ir(2)(CH(3))(CO)(3)(μ-C(H)CF(3))(dppm)(2)][CF(3)SO(3)]. Addition of hydrogen to the cis-difluorovinyl-bridged product results in the quantitative elimination of cis-difluoroethylene, while its reaction with CO yields a mixture of cis-difluoropropene and 2,3-difluoropropene by reductive elimination of the methyl and difluorovinyl groups with an accompanying isomerization in the case of the second product. Finally, protonation of the 2,2,2-trifluoroethylidene-bridged product liberates 1,1,1-trifluoroethane, in which one hydrogen (H(+)) is from the acid while the other hydrogen (H(-)) is derived from activation of the methyl group.

The activation of carbon disulfide by binuclear rhodium complexes and the structure of [Rh2Cl2(CO)(C2S4)(Ph2PCH2PPh2)2]

Abstract The reactions of trans -[RhCl(CO)(DPM)] 2 (1) (DPM  Ph 2 PCH 2 PPh 2 ) and [Rh 2 Cl 2 (μ-CO)(DPM) 2 ] (2) with CS 2 have been investigated and the final product of each reaction, [Rh 2 Cl 2 (CO)(C 2 S 4 )(DPM) 2 ] (3), has been structurally characterized by X-ray crystallography. A scheme for the reaction of 2 is presented based on monitoring the stepwise addition Of CS 2 using 31 P 1 H and 13 C 31 P{ 1 H} NMR and infrared spectroscopy. The scheme for the reaction of 1 is based on infrared and 31 P{ 1 H} NMR data and on analogies with the reaction of 2, and with the similar, well characterized reactions of 1 with SO2. Compound 3 crystallizes in the space group P2 1 / c with a 22.311(3) A, b  22.843(3) A, c  22.828(3) A, β  115.21(1)° and Z  8. Based on 5929 observed reflections the structure was refined to R  0.112 and R w  0.143 based on group refinement for the phenyl rings and isotropic refinement for all other non-hydrogen atoms. Slight differences in the geometries of the two independent dimers are observed resulting from different DPM phenyl ring orientations. However, the major features of the two dimers are the same, having a C 2 S 4 fragment bridging two quasi-octahedral rhodium atoms and bound by a sulfur (RhS (dimers AB Rh(1)Cl(1) 2.428(6), 2.455(6) A; Rh(2)Cl(2)  2.508(8), 2.527(8) A; Rh(2)C(1)O(1)  1.87(2), 1.96(3) A.

Synthesis of (μ3η2-vinylidene)(μ-CO)nonacarbonyltriiron complexes

Abstract Trinuclear vinylidene complexes of the type (μ 3 ,η 2 -CCHR 1 (μ-CO)Fe 3 (CO) 9 were prepared from the reactions of 1-bromoalkynes (R 1 CCBr) with [Et 3 NH][HFe 3 (CO) 11 ]. Structural assignment by the standard analytical and spectroscopic techniques was confirmed by the X-ray crystal structure determination of the phenyl derivative. This molecule, (μ 3 ,η 2 -CCHPh)(μ-CO)Fe 3 (CO) 9 crystallizes in the triclinic space group P 1 with a 9.254(2) A, b 12.717(3) A, c 9.114(1) A, α 102.15(2)°, β 100.84(1)°, γ 75.45(2)°, V 1004.4 A 3 and Z = 2. On the basis of 3147 unique observations and 280 parameters varied, the structure was refined by full-matrix, least-squares techniques to R = 0.031 and R w = 0.043. The three iron atoms form a near equilateral triangle with the vinylidene α carbon atoms bonded to all three iron centers by short FeC bonds (1.909(2), 1.917(2) and 2.009(2) A) but with the β carbon bonded only to the apical iron by an unusually long FeC bond (2.288(2) A). Presumably, formation of these products resulted from an intramolecular hyride migration to an initially formed acetylide intermediate.

Binuclear rhodium(I) compounds bridged by the bifunctional 2-mercaptothiazolinate anion

Reaction of [Rh(μ-S2NC3H4)(COD)]2 (1) with carbon monoxide yields the wine-red species [Rh(μ-S2NC3N4)(CO)2]2 (2). Addition of phosphine or phosphite ligands to solutions of 2 results in replacement of one carbonyl group on each metal to give [Rh(μ-S2NC3H4)(CO)(L)]2 (L = PPh3 (3), PMe3 (4), P(OPh)3 (5), P(OMe)3 (6)). Only the trans isomers of these compounds are observed. The structures of 3 and 4 have been determined by X-ray crystallography. Compound 3 crystallizes with two equivalents of THF in the triclinic space group P1 with a 10.973(1) A, b 12.142(2) A, c 20.611(3) A, α 76.62(1)°, β 80.41(1)°, γ 80.78(1)°, V 2613.0 A3 and Z = 2. On the basis of 7098 independent observations and 570 parameters varied the structure has refined to R = 0.035 and Rw = 0.057. In 3 the two square planar rhodium(I) centers are bridged in a head-to-tail arrangement by the two 2-mercaptothiazolinate groups, which are bound to the metals through the exocyclic sulfur and the nitrogen. The square planes are tilted to each other by 38.5° and the RhRh separation is 3.2435(3) A. Compound 4 crystallizes in the orthorhombic space group Pbca with a 10.032(2) A, b 28.335(5) A, c 17.126(2) A, V 4868.1 A3 and Z = 8 and has refined to R = 0.031 and Rw = 0.046 on the basis of 3682 independent observations and 235 parameters varied. The structure of 4 closely resembles that of 3 except that the tilt of the square planes is 30.0° and the RhRh separation has decreased to 3.0524(4) A.

Novel binuclear rhodium complexes containing ketonic carbonyl and acetylene ligands

Abstract The reaction of trans -[RhCl(CO)(DPM)] 2 (DPM = Ph 2 PCH 2 PPh 2 ) with dimethylacetylenedicarboxylate (DMA) and hexafluoro-2-butyne (HFB) yield the novel species [Rh 2 Cl 2 (μ-CO)(μ-Acet)(DPM) 2 ] (Acet = DMA, HFB). The X-ray structure determination of the DMA derivative indicates that the complex has the acetylene molecule coordinated as a cis -dimetallated olefin and also contains a ketonic carbonyl ligand. The long Rh⋯Rh separation (3.3542(9) A) suggests no metal—metal bond and the RhC(O)Rh angle (116.0(4)°) suggest sp 2 hybridization of the carbonyl carbon atom. Similarly the geometry at the acetylene ligand and the CC distance of the coordinated acetylene moiety (1.32(1) A) are consistent with the dimetallated olefinic formulation. This represents the first reported characterization of a ketonic carbonyl complex outside the Ni triad. These novel complexes have also been formed by the direct insertion of the acetylene molecules into the formal RhRh bond in [Rh 2 Cl 2 (μ-CO)(DPM) 2 ].

Facile Carbon–Fluorine Bond Activation and Subsequent Functionalisation of 1,1‐Difluoroethylene and Tetrafluoroethylene Promoted by Adjacent Metal Centres

The bridging fluoroolefin ligands in the complexes [Ir(2)(CH(3))(CO)(2)(μ-olefin)(dppm)(2)][OTf] (olefin = tetrafluoroethylene, 1,1-difluoroethylene; dppm = μ-Ph(2)PCH(2)PPh(2); OTf(-) = CF(3)SO(3)(-)) are susceptible to facile fluoride ion abstraction. Both fluoroolefin complexes react with trimethylsilyltriflate (Me(3)SiOTf) to give the corresponding fluorovinyl products by abstraction of a single fluoride ion. Although the trifluorovinyl ligand is bound to one metal, the monofluorovinyl group is bridging, bound to one metal through carbon and to the other metal through a dative bond from fluorine. Addition of two equivalents of Me(3)SiOTf to the tetrafluoroethylene-bridged species gives the difluorovinylidene-bridged product [Ir(2)(CH(3))(OTf)(CO)(2)(μ-OTf)(μ-C=CF(2))(dppm)(2)][OTf]. The 1,1-difluoroethylene species is exceedingly reactive, reacting with water to give 2-fluoropropene and [Ir(2)(CO)(2)(μ-OH)(dppm)(2)][OTf] and with carbon monoxide to give [Ir(2)(CO)(3)(μ-κ(1):η(2)-C≡CCH(3))(dppm)(2)][OTf] together with two equivalents of HF. The trifluorovinyl product [Ir(2)(κ(1)-C(2)F(3))(OTf)(CO)(2)(μ-H)(μ-CH(2))(dppm)(2)][OTf], obtained through single C-F bond activation of the tetrafluoroethylene-bridged complex, reacts with H(2) to form trifluoroethylene, allowing the facile replacement of one fluorine in C(2)F(4) with hydrogen.

Unusual ligand transformations initiated by dppm deprotonation in methylene-bridged Rh/Os complexes.

The reaction of [RhOs(CO)(3)(μ-CH(2))(dppm)(2)][CF(3)SO(3)] (dppm = μ-Ph(2)PCH(2)PPh(2)) with 1,3,4,5-tetramethylimidazol-2-ylidene (IMe(4)) results in competing substitution of the Rh-bound carbonyl by IMe(4) and dppm deprotonation by IMe(4) to give the two products [RhOs(IMe(4))(CO)(2)(μ-CH(2))(dppm)(2)][CF(3)SO(3)] and [RhOs(CO)(3)(μ-CH(2))(μ-κ(1):η(2)-dppm-H)(dppm)] [3; dppm-H = bis(diphenylphosphino)methanide], respectively. In the latter product, the dppm-H group is P-bound to Os while bound to Rh by the other PPh(2) group and the adjacent methanide C. The reaction of the tetracarbonyl species [RhOs(CO)(4)(μ-CH(2))(dppm)(2)][CF(3)SO(3)] with IMe(4) results in the exclusive deprotonation of a dppm ligand to give [RhOs(CO)(4)(μ-CH(2))(μ-κ(1):κ(1)-dppm-H)(dppm)] (4) in which dppm-H is P-bound to both metals. Both deprotonated products are cleanly prepared by the reaction of their respective precursors with potassium bis(trimethylsilyl)amide. Reversible conversion of the μ-κ(1):η(2)-dppm-H complex to the μ-κ(1):κ(1)-dppm-H complex is achieved by the addition or removal of CO, respectively. In the absence of CO, compound 3 slowly converts in solution to [RhOs(CO)(3)(μ-κ(1):κ(1):κ(1)-Ph(2)PCHPPh(2)CH(2))(dppm)] (5) as a result of dissociation of the Rh-bound PPh(2) moiety of the dppm-H group and its attack at the bridging CH(2) group. Compound 4 is also unstable, yielding the ketenyl- and ketenylidene/hydride tautomers [RhOs(CO)(3)(μ-κ(1):η(2)-CHCO)(dppm)(2)] (6a) and [RhOs(H)(CO)(3)(μ-κ(1):κ(1)-CCO)(dppm)(2)] (6b), initiated by proton transfer from μ-CH(2) to dppm-H. Slow conversion of these tautomers to a pair of isomers of [RhOs(H)(CO)(3)(μ-κ(1):κ(1):κ(1)-Ph(2)PCH(COCH)PPh(2))(dppm)] (7a and 7b) subsequently occurs in which proton transfer from a dppm group to the ketenylidene fragment gives rise to coupling of the resulting dppm-H methanide C and the ketenyl unit. Attempts to couple the ketenyl- or ketenylidene-bridged fragments in 6a/6b with dimethyl acetylenedicarboxylate (DMAD) yield [RhOs(κ(1)-CHCO)(CO)(3)(μ-DMAD)(dppm)(2)], in which the ketenyl group is terminally bound to Os.

‘Side-on’ co-ordination of a phenylhydrazido ligand: synthesis and X-ray structure determination of [(η5-C5H5)2W(H2NNPh)][BF4]

The low-temperature product, [(η5-C5H5)2WH(NNHR)][X](R = aryl, X = BF4 or PF6), from the reaction of [RN2][X] with (η5-C5H5)2WH2 rearranges in solution above –20 °C to yield [(η5-C5H5)2W(H2NNR)][X] in which the arylhydrazido ligand is bound to W in a ‘side-on’ or dihapto manner.